A method of fabricating a conventional uncooled infrared sensing unit requires dozens of manufacturing steps that are performed on an integrated circuit (IC) wafer and are not standard manufacturing steps required by the normal IC, thus posing challenges to obtain favorable yield and leading to difficulties in complying with the strict requirements for controlling additional manufacturing steps. Hence, based on the standard IC manufacturing process, the infrared sensing device and a reading circuit are integrated together, so as to improve the yield and ensure the benefit of economic of scale. Besides, the existing issues of the infrared sensing unit lie in the small effective light sensing region, the reduced efficiency of light absorption and conversion, and so forth. Hence, how to ensure the infrared sensing unit to achieve favorable light absorption and conversion efficiency and simplify the manufacturing process has become one of the important issues in terms of research and development.